Added support for GZIP compression for main HTML files

Hi everyone,

I have spent some time to finally come up with the solution for gzip support for main HTML files. Related issue https://github.com/socketstream/socketstream/pull/376

Works only for packed files, which does make cense.

I tested with default SocketStream demo app (http + connect) and with more advanced with [Express.js](https://github.com/visionmedia/express) on the top.

Results:
```
Date				Wed, 09 Oct 2013 19:59:55 GMT
Content-Encoding	gzip
Transfer-Encoding	chunked
Connection			keep-alive
Vary				Accept-Encoding
Content-Type		text/html
```

and with Express
```
Date				Wed, 09 Oct 2013 20:00:14 GMT
Content-Encoding	gzip
Transfer-Encoding	chunked
Connection			keep-alive
X-Powered-By		Express
Vary				Accept-Encoding
Content-Type		text/html
```